Intruding metal detection method for induction type power supply system and related supplying-end module

ABSTRACT

An intruding metal detection method for a supplying-end module of an induction type power supply system having a supplying-end coil includes interrupting at least one driving signal of the induction type power supply system to stop driving the supplying-end coil during a measurement period, to generate a coil signal of the supplying-end coil; measuring a plurality of peaks of the coil signal within a plurality of consecutive oscillation cycles of the coil signal, to obtain a plurality of peak trigger voltages, respectively; calculating a first attenuation parameter according to a first peak trigger voltage and a second peak trigger voltage among the plurality of peak trigger voltages; and comparing the first attenuation parameter with a first threshold value to determine whether there is an intruding metal existing in a power supply range of the induction type power supply system.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S.application Ser. No. 15/005,014, filed on Jan. 25, 2016, and acontinuation-in-part application of U.S. application Ser. No.15/231,795, filed on Aug. 9, 2016.

U.S. application Ser. No. 15/231,795 is further a continuation-in-partapplication of U.S. application Ser. No. 15/005,014, filed on Jan. 25,2016, and a continuation-in-part application of U.S. application Ser.No. 15/197,796, filed on Jun. 30, 2016.

U.S. application Ser. No. 15/197,796 is further a continuation-in-partapplication of U.S. application Ser. No. 14/822,875, filed on Aug. 10,2015, a continuation-in-part application of U.S. application Ser. No.14/731,421, filed on Jun. 5, 2015, and a continuation-in-partapplication of U.S. application Ser. No. 14/876,788, filed on Oct. 6,2015.

U.S. application Ser. No. 14/731,421 is further a continuation-in-partapplication of U.S. application Ser. No. 14/017,321, filed on Sep. 4,2013, and a continuation-in-part application of U.S. application Ser.No. 13/541,090, filed on Jul. 3, 2012.

U.S. application Ser. No. 14/017,321 is further a continuation-in-partapplication of U.S. application Ser. No. 13/541,090, filed on Jul. 3,2012, and a continuation-in-part application of U.S. application Ser.No. 13/212,564, filed on Aug. 18, 2011.

U.S. application Ser. No. 13/212,564 is further a continuation-in-partapplication of U.S. application Ser. No. 13/154,965, filed on Jun. 7,2011.

U.S. application Ser. No. 14/876,788 is further a continuation-in-partapplication of U.S. application Ser. No. 14/017,321, filed on Sep. 4,2013.

The contents of these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an intruding metal detection method,and more particularly, to an intruding metal detection method applicableto an induction type power supply system.

2. Description of the Prior Art

In an induction type power supply system, a power supply device appliesa driver circuit to drive a supplying-end coil to generate resonance, inorder to send electromagnetic waves. A coil of the power receivingdevice may receive the electromagnetic waves and perform powerconversion to generate DC power to be supplied for the device in thepower receiving end. If the electromagnetic energy sent by thesupplying-end coil is exerted on a metal, it may heat the metal. Theaccumulated heat energies may cause high temperature on the metal, whichmay burn surrounding objects and thus generate damages. In an inductiontype power supply system in the prior art, driving operation in thepower delivery process may be periodically interrupted to detect theintruding metal, and the intruding metal is determined based on themeasured slop variations. However, the output power of the supplying-endcoil may be adjusted at any time according to the distance between thesupplying-end device and the receiving-end device. For example, theoutput power may be larger with a farer coil distance, and the outputpower may be smaller with a nearer coil distance. With variations ofoutput power, the amplitude of the coil signal may also change, suchthat the attenuation patterns of resonant signals due to interrupteddriving of the coil may also be different. Therefore, when the outputpower changes, the supplying-end device needs to spend several detectioncycles to adjust the voltage setting of the comparator to track thesignal's peak values. If the coil voltage is unstable due to influencesof power or loading, it is hard to track the peak values to determinethe attenuation slope.

In addition, in order to determine the attenuation slope, the drivingsignal should be interrupted for a period of time. However, theoperations of interrupting the driving signal during wireless chargingmay reduce the entire power output capability. If the interrupting timeis excessively long, the power supply efficiency may be reduced. Also,recovery of the driving signal after the long interrupting time mayeasily generate excessive electromagnetic interference (EMI). In theprior art, a comparator module is applied to obtain multiple peakvoltage levels, so as to determine slope variations between multiplesections in the attenuation of the coil signal; hence, a longerinterrupting time may be required. Taking U.S. application Ser. No.15/231,795 as an example, 7-15 oscillation cycles of the coil arerequired to accomplish the measurement of four peak voltage levels todetermine the variations of attenuation slope.

Thus, there is a need to provide another intruding metal detectionmethod, which is capable of finishing metal detection within a shortinterrupting time of coil driving, and also preventing the variations ofoutput power or loading from influencing the detection results.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide anintruding metal detection method capable of finishing the metaldetection within a short interrupting time of coil driving, where thedetection of intruding metal may be accomplished in 2-3 coil oscillationcycles in minimum. In addition, the intruding metal detection method ofthe present invention may perform determination according to theattenuation ratio of the coil signal, which solves the problems in theprior art where the determination method based on attenuation slope iseasily influenced by the coil amplitude and the loading.

An embodiment of the present invention discloses an intruding metaldetection method for a supplying-end module of an induction type powersupply system. The supplying-end module comprises a supplying-end coil.The intruding metal detection method comprises interrupting at least onedriving signal of the induction type power supply system to stop drivingthe supplying-end coil during a measurement period, to generate a coilsignal of the supplying-end coil; measuring a plurality of peaks of thecoil signal within a plurality of consecutive oscillation cycles of thecoil signal, to obtain a plurality of peak trigger voltages,respectively; calculating a first attenuation parameter according to afirst peak trigger voltage and a second peak trigger voltage among theplurality of peak trigger voltages; and comparing the first attenuationparameter with a first threshold value to determine whether there is anintruding metal existing in a power supply range of the induction typepower supply system.

Another embodiment of the present invention discloses a supplying-endmodule for an induction type power supply system for performing anintruding metal detection method. The supplying-end module comprises asupplying-end coil, a resonant capacitor, at least one power driverunit, a signal receiver and a processor. The resonant capacitor, coupledto the supplying-end coil, is used for performing resonance togetherwith the supplying-end coil. The at least one power driver unit, coupledto the supplying-end coil and the resonant capacitor, is used forsending at least one driving signal to the supplying-end coil to drivethe supplying-end coil to generate energies, and interrupting the atleast one driving signal to stop driving the supplying-end coil during ameasurement period to generate a coil signal of the supplying-end coil.The signal receiver, coupled to the supplying-end coil, is used forreceiving the coil signal from the supplying-end coil. The processor,coupled to the signal receiver, is used for performing the followingsteps: measuring a plurality of peaks of the coil signal within aplurality of consecutive oscillation cycles of the coil signal, toobtain a plurality of peak trigger voltages, respectively; calculating afirst attenuation parameter according to a first peak trigger voltageand a second peak trigger voltage among the plurality of peak triggervoltages; and comparing the first attenuation parameter with a firstthreshold value to determine whether there is an intruding metalexisting in a power supply range of the induction type power supplysystem.

Another embodiment of the present invention discloses an intruding metaldetection method for a supplying-end module of an induction type powersupply system. The supplying-end module comprises a supplying-end coil.The intruding metal detection method comprises obtaining a previous peaktrigger voltage measured during a previous measurement period andsetting a reference voltage to be equal to the previous peak triggervoltage; interrupting at least one driving signal of the induction typepower supply system to stop driving the supplying-end coil during ameasurement period, to generate a coil signal of the supplying-end coil;measuring a first peak of the coil signal within an oscillation cycle ofthe coil signal, to obtain a first peak trigger voltage; comparing thefirst peak trigger voltage with the reference voltage; and determiningthat there is no intruding metal existing in a power supply range of theinduction type power supply system when the first peak trigger voltageis equal to or close to the reference voltage.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an induction type power supply systemaccording to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an intruding metal detection processaccording to an embodiment of the present invention.

FIG. 3 is a schematic diagram of stopping driving the supplying-end coilduring a measurement period.

FIGS. 4-7 are schematic diagrams of obtaining peak trigger voltagesduring a measurement period according to an embodiment of the presentinvention.

FIG. 8 is a schematic diagram of another intruding metal detectionprocess according to an embodiment of the present invention.

FIG. 9 is a schematic diagram of using a peak trigger voltage to performdetermination on the intruding metal during a measurement periodaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram of an inductiontype power supply system 100 according to an embodiment of the presentinvention. As shown in FIG. 1, the induction type power supply system100 includes a supplying-end module 1 and a receiving-end module 2. Thesupplying-end module 1 receives power from a power supply device 10 andoutputs wireless power to the receiving-end module 2. The supplying-endmodule 1 includes a supplying-end coil 16 and resonant capacitors 141and 142, disposed as a C-L-C structure. The supplying-end coil 16 isused for delivering electromagnetic energies to the receiving-end module2 to supply power. The resonant capacitors 141 and 142, coupled to thetwo terminals of the supplying-end coil 16, respectively, are used forperforming resonance together with the supplying-end coil 16 duringpower supply. In addition, in the supplying-end module 1, a magneticconductor 161 composed of magnetic materials may be selectivelydisposed, to enhance the electromagnetic induction capability of thesupplying-end coil 16 and also prevent electromagnetic energies fromaffecting the objects located in the non-inducting side of the coil.

In order to control the operations of the supplying-end coil 16 and theresonant capacitors 141 and 142, the supplying-end module 1 furtherincludes a processor 111, a clock generator 112, power driver units 121and 122, a signal receiver 120 and a voltage dividing circuit 130. Thepower driver units 121 and 122, coupled to the supplying-end coil 16 andthe resonant capacitors 141 and 142, are used for sending drivingsignals D1 and D2 to the supplying-end coil 16, respectively. The powerdriver units 121 and 122 may be controlled by the processor 111, fordriving the supplying-end coil 16 to generate and send power. When thepower driver units 121 and 122 are both active, full-bridge driving isperformed. In another embodiment, only one of the power driver units 121and 122 is active or only one of the power driver units 121 and 122 isdisposed, which leads to half-bridge driving. The clock generator 112,coupled to the power driver units 121 and 122, is used for controllingthe power driver units 121 and 122 to send the driving signals D1 andD2. The clock generator 112 may be a pulse width modulation (PWM)generator or other type of clock generator, for outputting a clocksignal to the power driver units 121 and 122. The processor 111 mayreceive information related to a coil signal C1 (i.e., the voltagesignal between the supplying-end coil 16 and the resonant capacitor 142)from the supplying-end coil 16, such as the resonant frequency orattenuation degree of the coil signal C1, and determine whether there isan intruding metal accordingly. The processor 111 may be a centralprocessing unit (CPU), a microprocessor, a micro controller unit (MCU),or other type of processing device or computation device. The signalreceiver 120 is used for tracking the resonant frequency and the peakvalues of the coil signal C1, and providing information related to theresonant frequency and the peak values for the processor 111 forfollow-up interpretation. The voltage dividing circuit 130, whichincludes voltage dividing resistors 131 and 132, may attenuate the coilsignal C1 on the supplying-end coil 16 and then output the coil signalC1 to the processor 111 and the signal receiver 120. In someembodiments, if the tolerance voltage of the circuits such as theprocessor 111 and the signal receiver 120 is high enough, the voltagedividing circuit 130 may not be disposed and the processor 111 maydirectly receive the coil signal C1 from the supplying-end coil 16.Other possible components or modules such as a power supply unit anddisplay unit may be included or not according to system requirements.These components are omitted herein without affecting the illustrationsof the present embodiments.

In an embodiment, the signal receiver 120 includes a voltage generator113 and a comparator 114, as shown in FIG. 1. The voltage generator 113may be a digital to analog converter (DAC), which may receive theinformation of a reference voltage from the processor 111, and convertit into an analog voltage and then output the analog voltage. An inputterminal of the comparator 114 may receive a reference voltage, andanother input terminal of the comparator 114 may receive the coil signalC1 from the supplying-end coil 16, so as to compare the coil signal C1with the reference voltage. The processor 111 then performs follow-updetermination and signal processing operations according to the abovecomparison result. Note that the signal receiver 120 may also beintegrated in the processor 111, and the implementation method is notlimited herein.

Please keep referring to FIG. 1. The receiving-end module 2 includes aload unit 21, a capacitor 22, a rectification circuit 230, areceiving-end coil 26 and resonant capacitors 241 and 242. In thereceiving-end module 2, a magnetic conductor 261 composed of magneticmaterials may also be selectively disposed, to enhance theelectromagnetic induction capability of the receiving-end coil 26 andalso prevent electromagnetic energies from affecting the objects locatedin the non-inducting side of the coil. The receiving-end coil 26 mayreceive electric power from the supplying-end coil 16 and send thereceived power to the rectification circuit 230 for rectification. Afterthe rectification is accomplished, the power is transmitted to thecapacitor 22 and the load unit 21 at the back end. The capacitor 22 maybe a filter capacitor for performing filtering, a regulating capacitorfor stabilizing the output voltage, or their combinations; this shouldnot be limited herein. In the receiving-end module 2, other possiblecomponents or modules such as a feedback circuit and receiving-endmicroprocessor may be included or not according to system requirements.These components are omitted herein without affecting the illustrationsof the present embodiments.

In addition, an intruding metal 3 is not included in the induction typepower supply system 100, but is illustrated between the supplying-endmodule 1 and the receiving-end module 2 in FIG. 1 to facilitate thedescription. When the intruding metal 3 is located in a power supplyrange of the induction type power supply system 100, the intruding metal3 may receive electromagnetic energies sent by the supplying-end module1 and thus be heated. The intruding metal detection method of thepresent invention is configured to determine whether there is anintruding metal 3 existing in the power supply range of the inductiontype power supply system 100, and stop sending power when determiningthat the intruding metal 3 exists.

Different from the prior art where the supplying-end module determinesan intruding metal by measuring the variations of attenuation slope ofthe coil, the present invention performs determination on intrudingmetal by measuring the ratio of voltage attenuation of the coil signal.Please refer to FIG. 2, which is a schematic diagram of an intrudingmetal detection process 20 according to an embodiment of the presentinvention. As shown in FIG. 2, the intruding metal detection process 20,which may be utilized in a supplying-end device of an induction typepower supply system such as the supplying-end module 1 of the inductiontype power supply system 100 shown in FIG. 1, includes the followingsteps:

Step 200: Start.

Step 202: Interrupt the driving signals D1 and D2 of the induction typepower supply system 100 to stop driving the supplying-end coil 16 duringa measurement period, to generate a coil signal C1 of the supplying-endcoil 16.

Step 204: Measure two peaks of the coil signal C1 within two consecutiveoscillation cycles of the coil signal C1, to obtain two peak triggervoltages, respectively.

Step 206: Calculate an attenuation parameter according to the two peaktrigger voltages.

Step 208: Compare the attenuation parameter with a correspondingthreshold value and determine whether the attenuation parameter isgreater than the threshold value. If yes, go to Step 216; otherwise, goto Step 210.

Step 210: Determine whether the number of measured oscillation cyclesreaches a predetermined number. If yes, go to Step 216; otherwise, go toStep 212.

Step 212: Measure a peak of the coil signal C1 within the nextoscillation cycle of the coil signal C1, to obtain a peak triggervoltage.

Step 214: Calculate an attenuation parameter according to the peaktrigger voltage and another peak trigger voltage obtained in theprevious oscillation cycle.

Step 216: Average the obtained attenuation parameters to generate anaverage result, and compare the average result with a basic thresholdvalue to determine whether the average result is greater than the basicthreshold value. If yes, go to Step 218; otherwise, go to Step 220.

Step 218: Determine that there is no intruding metal 3 existing in thepower supply range of the induction type power supply system 100.

Step 220: Determine that there is an intruding metal 3 existing in thepower supply range of the induction type power supply system 100.

Step 222: End.

According to the intruding metal detection process 20, in thesupplying-end module 1 of the induction type power supply system 100,the driving signals D1 and D2 may be interrupted for a period of timeduring the driving operation. At this moment, the power driver units 121and 122 may stop driving the supplying-end coil 16. When thesupplying-end coil 16 stops driving, the coil signal C1 may keeposcillating and attenuate gradually since there are still energiesexisting between the supplying-end coil 16 and the resonant capacitors141 and 142. As shown in FIG. 3, when driving is stopped, the drivingsignals D1 and D2 stay in the high voltage level and the low voltagelevel for a period of time, respectively. At this moment, the coilsignal C1 appears to have an oscillating and attenuating waveform.Afterwards, the power driver units 121 and 122 are reconnected to outputthe square-wave driving signals D1 and D2 to drive the supplying-endcoil 16 to output power again. In another embodiment, the drivingsignals D1 and D2 may be controlled to simultaneously stay in the highvoltage level or simultaneously stay in the low voltage level to stopdriving, and this is not limited herein. The abovementioned period wherethe driving signals D1 and D2 are interrupted is configured formeasuring the resonance of the coil signal C1 to perform detection ofthe intruding metal 3, and will be called “measurement period”hereinafter for easy understanding.

During the measurement period, a plurality of consecutive oscillationcycles exist in the coil signal C1. The processor 111 may measure thepeaks of the coil signal C1 within the plurality of oscillation cycles,to obtain a plurality of peak trigger voltages, respectively. Pleaserefer to FIG. 4, which is a schematic diagram of obtaining peak triggervoltages VB and VC during a measurement period according to anembodiment of the present invention. As shown in FIG. 4, the coil signalC1 includes three peaks A, B and C during the measurement period. Sincethe first peak A occurs in the time period when the driving signals D1and D2 just stop driving, the oscillation at the peak A may stillinfluenced by the driving signals D1 and D2 and may not be considered asintrinsic oscillation of the supplying-end coil 16; hence, the height ofthe peak A may not reach the height of intrinsic oscillation. In such acondition, in order to prevent that determination of the intruding metal3 is influenced by the driving signals D1 and D2 and thus getsdistorted, the measurement of the peak trigger voltage of the peak A maybe omitted, and only the peak trigger voltages VB and VC of the peaks Band C are measured.

In an oscillation cycle for measuring a peak, the processor 111 may seta reference voltage (illustrated as a dotted line in FIG. 4). Thevoltage generator 113 may output the reference voltage to the comparator114, and the comparator 114 may compare the reference voltage with thecoil signal C1 to generate a comparison result CP1. In detail, beforeentering the oscillation cycle corresponding to the peak B, theprocessor 111 may preset the reference voltage to be equal to a triggerinitiation voltage V0_B. Subsequently, after the voltage level of thecoil signal C1 rises above the reference voltage to generate a triggersignal at the output terminal of the comparator 114 (i.e., a highvoltage level appears in the comparison result CP1), the processor 111may control the reference voltage to rise gradually. When the referencevoltage reaches the voltage level of the coil signal C1, the processor111 may determine that the trigger signal ends (i.e., the comparisonresult CP1 returns to the low voltage level). At this moment, theprocessor 111 may obtain the level of the reference voltage as the peaktrigger voltage VB corresponding to the peak B. Similarly, for theoscillation cycle corresponding to the peak C, the processor 111 maypreset the reference voltage to be equal to a trigger initiation voltageV0_C, and thereby obtain the peak trigger voltage VC corresponding tothe peak C in the same manner.

Subsequently, the processor 111 may calculate a first attenuationparameter PAR1 according to the peak trigger voltage VB and the peaktrigger voltage VC. In detail, the first attenuation parameter PAR1 maybe a ratio of the average of the peak trigger voltage VB and the peaktrigger voltage VC relative to the difference of the peak triggervoltage VB and the peak trigger voltage VC. In an embodiment, theprocessor 111 may calculate the summation result of the peak triggervoltage VB and the peak trigger voltage VC divided by the subtractionresult of the peak trigger voltage VB and the peak trigger voltage VC toobtain the first attenuation parameter PAR1, and the detailedcalculation is shown below:

${{PAR}\; 1} = \frac{{VB} + {VC}}{{VB} - {VC}}$

Please note that, in U.S. application Ser. No. 15/231,795, determinationof the intruding metal is performed using the variations of attenuationslope, i.e., the variations of attenuation quantities. However, in thesituation where no intruding metal exists, the attenuation quantity maybe larger after interruption of coil driving if the output power ishigher (i.e., the amplitude of the coil signal C1 is larger); and theattenuation quantity may be smaller after interruption of coil drivingif the output power is lower (i.e., the amplitude of the coil signal C1is smaller). That is, the attenuation quantity and the output power mayvary with a substantially identical ratio. For example, in the situationwhere no intruding metal exists, if the peak trigger voltage VB is equalto 100 units of voltage, the peak trigger voltage VC may beapproximately equal to 90 units of voltage; and if the peak triggervoltage VB is equal to 50 units of voltage, the peak trigger voltage VCmay be approximately equal to 45 units of voltage. The attenuationquantities of peak values are different in these two cases. Therefore,in the present invention, the ratio of the average or summation of thepeak trigger voltages relative to the difference (i.e., the attenuationquantity) of the peak trigger voltages is applied to calculate theattenuation parameter. The calculation method eliminates the influenceon attenuation of the coil signal from the output power, in order toachieve more effective determination of intruding metal. In thisembodiment, a larger attenuation parameter stands for a slowerattenuation speed, which means the intruding metal is less probably toexist; and a smaller attenuation parameter stands for a fasterattenuation speed, which means the intruding metal is more probably toexist.

It should also be noted that a peak trigger voltage is always unequal tothe peak voltage of the corresponding peak. In fact, the peak triggervoltage is slightly lower than the peak voltage of the correspondingpeak. As shown in FIG. 4, the peak trigger voltage VB is close to andslightly lower than the voltage of the peak B, and the peak triggervoltage VC is close to and slightly lower than the voltage of the peakC. The trigger initiation voltages V0_B and V0_C are set to valuesslightly lower than the voltage levels of the peak B and the peak C,respectively; hence, the reference voltage after rising may intersectthe coil signal C1 at the right-hand side of the peak, such that thepeak trigger voltages VB and VC obtained based on the reference voltagemay also be slightly lower than and close to the corresponding peakvoltages, respectively. In addition, according to the above calculationmethod of the attenuation parameter, the value of the attenuationparameter is mainly influenced by the attenuation ratio. Therefore, ifthe peak trigger voltages slightly lower than the peak voltages areapplied as the calculation basis, the obtained determination result ofintruding metal is substantially identical to the determination resultobtained based on the peak voltages. As long as the attenuationparameter may reflect the attenuation quantity or attenuation ratio, theattenuation parameter is feasible to determine the intruding metal 3.

As mentioned above, the first attenuation parameter PAR1 is equal to thesummation result of the peak trigger voltage VB and the peak triggervoltage VC divided by the subtraction result of the peak trigger voltageVB and the peak trigger voltage VC. After the first attenuationparameter PAR1 is obtained, the processor 111 may set a first thresholdvalue TH1 and compare the first attenuation parameter PAR1 with thefirst threshold value TH1 to determine whether there is an intrudingmetal 3 existing in a power supply range of the induction type powersupply system 100. In an embodiment, when the first attenuationparameter PAR1 is greater than the first threshold value TH1, theprocessor 111 may determine that there is no intruding metal 3 existingin the power supply range of the induction type power supply system 100;and when the first attenuation parameter PAR1 is smaller than the firstthreshold value TH1, the processor 111 further performs follow-updetermination. In the induction type power supply system, there arelarge noises in the power supply terminal and/or the loading terminal,and the noises may easily interfere with analysis and detection of thecoil signal. Therefore, the related data or determination result ofintruding metal should be obtained by more times to accurately determinethe intruding metal, in order to avoid wrong determination of intrudingmetal to erroneously disable the power output function due to noiseinterference.

In an embodiment, the processor 111 may set a basic threshold value TH0.During the testing process of induction type power supply products, theattenuation parameter may vary between different products and differentenvironments. The basic threshold value TH0 may be set according to thelowest attenuation parameter measured without existence of any intrudingmetal. Preferably, the basic threshold value TH0 may be set to a lowervalue with a broader determination criterion, to prevent noiseinterference from being wrongly determined to be an intruding metal. Theprocessor 111 then adds different values to the basic threshold valueTH0 to obtain a plurality of threshold values, respectively, such as thefirst threshold value TH1, the second threshold value TH2, and the thirdthreshold value TH3. The processor 111 may compare the first attenuationparameter PAR1, the second attenuation parameter PAR2, the thirdattenuation parameter PAR3 and the fourth attenuation parameter PAR4obtained during a measurement period with the first threshold value TH1,the second threshold value TH2, the third threshold value TH3 and thebasic threshold value TH0, respectively, to perform determination on theintruding metal 3. For example, the processor 111 may set the basicthreshold value TH0 to 150. The processor 111 then sets that the firstthreshold value TH1 is equal to the basic threshold value TH0=150 plus30, i.e., 180; the second threshold value TH2 is equal to the basicthreshold value TH0=150 plus 20, i.e., 170; and the third thresholdvalue TH3 is equal to the basic threshold value TH0=150 plus 10, i.e.,160. In this embodiment, the first threshold value TH1 is greater thanthe second threshold value TH2, and the second threshold value TH2 isgreater than the third threshold value TH3.

First, the processor 111 compares the first attenuation parameter PAR1with the first threshold value TH1. In an embodiment (as shown in Table1), the processor 111 may obtain the peak trigger voltage VB equal to1000 units of voltage and the peak trigger voltage VC equal to 990 unitsof voltage. After calculation, the first attenuation parameter PAR1 isobtained as 199. The first attenuation parameter PAR1=199 is greaterthan the first threshold value TH1=180, which means that the firstattenuation parameter is far greater than the basic threshold value TH0.Therefore, the processor 111 determines that no intruding metal 3exists.

TABLE 1 Peak/Oscillation cycle B C × × × Peak trigger voltage 1000 990 ×× × Attenuation parameter 199 × × × Threshold value 180 170 160 150

In this embodiment, the first attenuation parameter PAR1 is greater thanthe first threshold value TH1 and is far greater than the basicthreshold value TH0, which means that the probability that an intrudingmetal 3 exists is quite low, and the system is quite safe; hence, theprocessor 111 directly determines that there is no intruding metal 3. Insuch a condition, determination of the intruding metal 3 may beaccomplished with only 2 oscillation cycles measured by the processor111. In other words, the measurement period during which the drivingsignals D1 and D2 interrupt may only include 3 oscillation cycles,wherein no measurement is performed in the oscillation cyclecorresponding to the peak A, and determination of the intruding metal 3is accomplished after peak measurements in the oscillation cyclescorresponding to the peaks B and C are accomplished and the firstattenuation parameter PAR1 is obtained.

In an embodiment, the first attenuation parameter PAR1 is smaller thanthe first threshold value TH1. At this moment, the processor 111 furtherperforms follow-up determination of the intruding metal 3, as shown inTable 2.

TABLE 2 Peak/Oscillation cycle B C D × × Peak trigger voltage 1000 988977 × × Attenuation parameter 166 179 × × Threshold value 180 170 160150

In detail, the processor 111 first compares the first attenuationparameter PAR1 with the first threshold value TH1. After determiningthat the first attenuation parameter PAR1=166 is smaller than the firstthreshold value TH1=180, the processor 111 may measure the nextoscillation cycle of the coil signal C1 (i.e., the oscillation cyclecorresponding to the peak D). As shown in FIG. 5, within the oscillationcycle of the peak D, the processor 111 may preset the reference voltageto be equal to a trigger initiation voltage V0_D, and obtain the peaktrigger voltage VD corresponding to the peak D according to the abovemethod. The processor 111 then calculates a second attenuation parameterPAR2 according to the peak trigger voltage VC and the peak triggervoltage VD. In detail, the processor 111 may calculate the summationresult of the peak trigger voltage VC and the peak trigger voltage VDdivided by the subtraction result of the peak trigger voltage VC and thepeak trigger voltage VD to obtain the second attenuation parameter PAR2,and the detailed calculation is shown below:

${{PAR}\; 2} = \frac{{VC} + {VD}}{{VC} - {VD}}$

In this embodiment, the peak trigger voltage VC is equal to 988 units ofvoltage and the peak trigger voltage VD is equal to 977 units ofvoltage. After calculation, the second attenuation parameter PAR2 isobtained as 179 (rounded to the nearest integer). The processor 111 thencompares the second attenuation parameter PAR2 with the second thresholdvalue TH2, and determines that the second attenuation parameter PAR2=179is greater than the second threshold value TH2=170. In such a condition,the processor 111 stops measuring the subsequent oscillation cycles inthis measurement period. Further, the processor 111 averages the firstattenuation parameter PAR1 and the second attenuation parameter PAR2obtained in the measurement period, and compares the above averageresult with the basic threshold value TH0 to perform determination onthe intruding metal 3. In this embodiment, the average value of thefirst attenuation parameter PAR1 and the second attenuation parameterPAR2 is greater than the basic threshold value TH0. Therefore, theprocessor 111 determines that there is no intruding metal 3 existing inthe power supply range of the induction type power supply system 100.

In another embodiment, the second attenuation parameter PAR2 may besmaller than the second threshold value TH2. At this moment, theprocessor 111 further performs follow-up determination of the intrudingmetal 3, as shown in Table 3.

TABLE 3 Peak/Oscillation cycle B C D E × Peak trigger voltage 1000 986974 962 × Attenuation parameter 142 163 161 × Threshold value 180 170160 150

In detail, the processor 111 first compares the first attenuationparameter PAR1 with the first threshold value TH1. After determiningthat the first attenuation parameter PAR1=142 is smaller than the firstthreshold value TH1=180, the processor 111 may measure the nextoscillation cycle of the coil signal C1 (i.e., the oscillation cyclecorresponding to the peak D) to obtain the second attenuation parameterPAR2, and compare the second attenuation parameter PAR2 with the secondthreshold value TH2. Subsequently, after determining that the secondattenuation parameter PAR2=163 is smaller than the second thresholdvalue TH2=170, the processor 111 may measure the next oscillation cycleof the coil signal C1 (i.e., the oscillation cycle corresponding to thepeak E). As shown in FIG. 6, within the oscillation cycle of the peak E,the processor 111 may preset the reference voltage to be equal to atrigger initiation voltage V0_E, and obtain the peak trigger voltage VEcorresponding to the peak E according to the above method. The processor111 then calculates a third attenuation parameter PAR3 according to thepeak trigger voltage VD and the peak trigger voltage VE. In detail, theprocessor 111 may calculate the summation result of the peak triggervoltage VD and the peak trigger voltage VE divided by the subtractionresult of the peak trigger voltage VD and the peak trigger voltage VE toobtain the third attenuation parameter PAR3, and the detailedcalculation is shown below:

${{PAR}\; 3} = \frac{{VD} + {VE}}{{VD} - {VE}}$

In this embodiment, the peak trigger voltage VD is equal to 974 units ofvoltage and the peak trigger voltage VE is equal to 962 units ofvoltage. After calculation, the third attenuation parameter PAR3 isobtained as 161 (rounded to the nearest integer). The processor 111 thencompares the third attenuation parameter PAR3 with the third thresholdvalue TH3, and determines that the third attenuation parameter PAR3=161is greater than the third threshold value TH3=160. In such a condition,the processor 111 stops measuring the subsequent oscillation cycles inthis measurement period. Further, the processor 111 averages the firstattenuation parameter PAR1, the second attenuation parameter PAR2 andthe third attenuation parameter PAR3 obtained in the measurement period,and compares the above average result with the basic threshold value TH0to perform determination on the intruding metal 3. In this embodiment,the average value of the first attenuation parameter PAR1, the secondattenuation parameter PAR2 and the third attenuation parameter PAR3 isgreater than the basic threshold value TH0. Therefore, the processor 111determines that there is no intruding metal 3 existing in the powersupply range of the induction type power supply system 100.

In another embodiment, the third attenuation parameter PAR3 may besmaller than the third threshold value TH3. At this moment, theprocessor 111 further performs follow-up determination of the intrudingmetal 3, as shown in Table 4.

TABLE 4 Peak/Oscillation cycle B C D E F Peak trigger voltage 1000 984968 952 936 Attenuation parameter 124 122 120 118 Threshold value 180170 160 150

In detail, the processor 111 first compares the first attenuationparameter PAR1 with the first threshold value TH1. After determiningthat the first attenuation parameter PAR1=124 is smaller than the firstthreshold value TH1=180, the processor 111 may measure the nextoscillation cycle of the coil signal C1 (i.e., the oscillation cyclecorresponding to the peak D) to obtain the second attenuation parameterPAR2, and compare the second attenuation parameter PAR2 with the secondthreshold value TH2. Subsequently, after determining that the secondattenuation parameter PAR2=122 is smaller than the second thresholdvalue TH2=170, the processor 111 may measure the next oscillation cycleof the coil signal C1 (i.e., the oscillation cycle corresponding to thepeak E) to obtain the third attenuation parameter PAR3, and compare thethird attenuation parameter PAR3 with the third threshold value TH3.Subsequently, after determining that the third attenuation parameterPAR3=120 is smaller than the third threshold value TH3=160, theprocessor 111 may measure the next oscillation cycle of the coil signalC1 (i.e., the oscillation cycle corresponding to the peak F). As shownin FIG. 7, within the oscillation cycle of the peak F, the processor 111may preset the reference voltage to be equal to a trigger initiationvoltage V0_F, and obtain the peak trigger voltage VF corresponding tothe peak F according to the above method. The processor 111 thencalculates a fourth attenuation parameter PAR4 according to the peaktrigger voltage VE and the peak trigger voltage VF. In detail, theprocessor 111 may calculate the summation result of the peak triggervoltage VE and the peak trigger voltage VF divided by the subtractionresult of the peak trigger voltage VE and the peak trigger voltage VF toobtain the fourth attenuation parameter PAR4, and the detailedcalculation is shown below:

${{PAR}\; 4} = \frac{{VE} + {VF}}{{VE} - {VF}}$

In this embodiment, the peak trigger voltage VE is equal to 952 units ofvoltage and the peak trigger voltage VF is equal to 936 units ofvoltage. After calculation, the fourth attenuation parameter PAR4 isobtained as 118. Since the number of oscillation cycles measured by theprocessor 111 in this measurement period reaches a predetermined number,the processor 111 may average the first attenuation parameter PAR1, thesecond attenuation parameter PAR2, the third attenuation parameter PAR3and the fourth attenuation parameter PAR4 obtained in the measurementperiod, and compare the above average result with the basic thresholdvalue TH0 to perform determination on the intruding metal 3. In thisembodiment, the average value of the first attenuation parameter PAR1,the second attenuation parameter PAR2, the third attenuation parameterPAR3 and the fourth attenuation parameter PAR4 is smaller than the basicthreshold value TH0. Therefore, the processor 111 determines that thereis an intruding metal 3 existing in the power supply range of theinduction type power supply system 100.

In the above embodiment, the measurement period where the drivingsignals D1 and D2 interrupt only includes 3-6 oscillation cycles torealize the determination of intruding metal 3. In comparison with U.S.application Ser. No. 15/231,795 where 7-15 oscillation cycles of coilare required to accomplish the measurement of four peak voltage levelsto determine the variations of attenuation slope, the intruding metaldetection method of the present invention may be realized within ashorter period of time, which further shortens the interrupting time ofthe driving signals D1 and D2. In general, in the situation where nointruding metal 3 exists and the coil signal C1 is not interfered withby noises, the obtained first attenuation parameter PAR1 may always begreater than the basic threshold value TH0. At this moment, only twooscillation cycles need to be measured to accomplish the determinationof intruding metal 3, and after the determination is accomplished, thecircuits of the power driver units 121 and 122 may be reconnectedimmediately to resend the driving signals D1 and D2, as shown in FIG. 3.On the other hand, only when an approaching metal or noise interferencecauses that the attenuation parameter falls, the processor 111 isrequired to measure more oscillation cycles. In other words, the smallerattenuation parameter means that an intruding metal is more probably toexist, and thus the number of measured oscillation cycles may also beincreased. No matter how many oscillation cycles are measured or howmany attenuation parameters are obtained finally, the processor 111 mayaverage all of the obtained attenuation parameter(s) and compare theaverage result with the basic threshold value TH0 to determine whetheran intruding metal 3 exists. In general, when driving of the coil isstopped, the coil signal may resonate intrinsically. If no intrudingmetal exists, the value of the attenuation slope of the coil signalrelative to the amplitude of the coil signal possesses a smallvariation. Since each attenuation parameter is calculated according tothe peak trigger voltages of adjacent oscillation cycles using the samemethod, the values of the attenuation parameters may be quite stable. Inthe induction type power supply system, signal determination may beinfluenced by power noises or circuit noises, but most of the powernoises and circuit noises may only generate a small variation on thevalues of the attenuation parameters; hence, the attenuation parametermay always be greater than the above threshold value so that thedetermination result will not be influenced. On the contrary, when anintruding metal appears, the peak trigger voltage may be attenuatedrapidly, and the attenuation parameter may fall rapidly due to the abovecalculation of dividing the summation result by the subtraction result,so that the detection and determination of the intruding metal may beperformed effectively.

During each measurement period, the number of measured oscillationcycles may be determined according to the comparison result of theattenuation parameter(s) and the corresponding threshold value(s), andthe average value of all attenuation parameter(s) may be obtained todetermine the intruding metal. In general, when any one of the first,second and third attenuation parameters PAR1-PAR3 is greater than thecorresponding threshold value, the calculation of the fourth attenuationparameter PAR4 will not be performed. The first, second and thirdthreshold values TH1-TH3 are all greater than the basic threshold valueTH0; hence, if the fourth attenuation parameter PAR4 is not calculated,the average of the previous three attenuation parameters PAR1-PAR3 mayusually be greater than the basic threshold value TH0, which leads tothe determination result that no intruding metal 3 exists. In such acondition, the processor 111 may determine the number of obtainedattenuation parameters or the number of measured oscillation cycles.Only when the number of obtained attenuation parameters reaches apredefined value (e.g., four attenuation parameters), the processor 111calculates the average of the attenuation parameters to performdetermination on the intruding metal 3. If the number of obtainedattenuation parameters does not reach the predefined value, theprocessor 111 may directly determine that there is no existing intrudingmetal 3.

In addition, in order to enhance the accuracy of determination and alsoprevent the power output function from being turned off due to wrongdetermination, the processor 111 may configure a counter for intrudingmetal. If the average of attenuation parameters obtained during ameasurement period is smaller than the basic threshold value, thecounter may be added by 1. When the counter for intruding metal reachesa specific value within a predetermined period, the processor 111determines that there is an existing intruding metal 3. Alternatively,the processor 111 may determine that there is an existing intrudingmetal 3 when the average value of attenuation parameters is determinedto be smaller than the basic threshold value in several consecutivemeasurement periods.

Please note that, in the above embodiment, the processor 111 first setsa reference voltage to be equal to a trigger initiation voltage,controls the reference voltage to rise when a trigger signal appears atthe output terminal of the comparator 114, and then obtains the level ofthe reference voltage at the end of the trigger signal as the peaktrigger voltage. In order to let the peak trigger voltage to effectivelyreflect the voltage level of the corresponding peak, the triggerinitiation voltage should be set to a level close to and slightly lowerthan the peak voltage, to successfully generate a trigger signal andalso make the peak trigger voltage more close to the peak voltage level.If the trigger initiation voltage is too high, the trigger initiationvoltage may be higher than the peak voltage and may not successfullytrigger. If the trigger initiation voltage is too low, the peak triggervoltage may be too low and may not reflect the actual magnitude of thepeak voltage even if the trigger may be successful.

In an embodiment, the processor 111 may calculate the trigger initiationvoltage(s) applied in the present measurement period according tocorresponding previous peak trigger voltage(s) obtained in the previousmeasurement period. For example, the processor 111 may set a triggerinitiation voltage to a value equal to the previous peak trigger voltageminus a predefined voltage value. Taking the oscillation cycle of thepeak B as an example, if the peak trigger voltage VB obtained in theprevious measurement period is equal to 1000 units of voltage, thetrigger initiation voltage V0_B in the present measurement period may beset to be 900 units of voltage (i.e., 1000 minus a predefined voltagevalue 100). Taking the oscillation cycle of the peak C as an example, ifthe peak trigger voltage VC obtained in the previous measurement periodis equal to 980 units of voltage, the trigger initiation voltage V0_C inthe present measurement period may be set to be 880 units of voltage(i.e., 980 minus the predefined voltage value 100). According to thepeak trigger voltage in the previous measurement period, the processor111 may know a possible level of the peak voltage, and thus set thetrigger initiation voltage to a slightly lower voltage level. The lowerlevel of the trigger initiation voltage may increase the occurrenceprobability of trigger signal. Unless the peak voltage falls rapidly,the signal trigger may appear to obtain the determination result ofintruding metal under most conditions.

In U.S. application Ser. No. 15/231,795, the method of determining peakvoltage levels is performed by determining whether to increase ordecrease the reference voltage according to whether there is a triggerin the previous measurement period, and determining that the referencevoltage keeps at the peak voltage level when trigger appears sometimesand no trigger appears sometimes during several consecutive measurementperiods. Therefore, without any variations on the loading and outputpower, a certain number of measurement periods are required to let thereference voltage to remain at the peak voltage level. In comparison,according to the method of obtaining peak trigger voltages of thepresent invention, the trigger initiation voltage is set to a lowervoltage level to increase the occurrence probability of trigger signals.In such a situation, the attenuation parameter may be calculated toperform determination on intruding metal immediately as long as atrigger occurs; hence, in the present invention, determination may berapidly finished without multiple measurement periods for tying the peakvoltage level to the coil peak. In addition, the trigger initiationvoltages may be continuously adjusted to preferable voltage levelsduring the determination process. For example, the trigger initiationvoltage V0_B in the present measurement period is set to 900 units ofvoltage and the trigger signal ends when the reference voltage rises to910 units of voltage, which means that the peak falls such that the peaktrigger voltage VB falls to 910 units of voltage. In such a condition,the trigger initiation voltage V0_B in the next measurement period maybe set to 810 units of voltage (i.e., 910 minus the predefined voltagevalue 100) to achieve preferable trigger effect and also increase theprobability of successful trigger.

Please note that sometimes the processor 111 may not be able to obtainthe corresponding peak trigger voltage in the previous measurementperiod. For example, during the previous measurement period, theprocessor 111 calculates the first attenuation parameter PAR1 accordingto the peak trigger voltage VB and the peak trigger voltage VC, anddetermines that the first attenuation parameter PAR1 is greater than thefirst threshold value TH1; hence, it is not necessary to measuresubsequent oscillation cycles and to calculate other attenuationparameters. However, in the present measurement period, the processor111 determines that the first attenuation parameter PAR1 is smaller thanthe first threshold value TH1 and thus measurement of subsequentoscillation cycle is required. In other words, the trigger initiationvoltage V0_D corresponding to the peak D should be determined in thepresent measurement period, but the oscillation cycle of the peak D isnot measured in the previous measurement period such that no peaktrigger voltage VD may be considered as a basis to calculate or estimatethe present trigger initiation voltage V0_D. In such a condition, theprocessor 111 may apply another previous peak trigger voltage of theprevious oscillation cycle in the present measurement period (i.e., thepeak trigger voltage VC corresponding to the peak C) as the basis, andestimate that the peak trigger voltage VD corresponding to the peak Dmay be lower than the peak trigger voltage VC by a specific level, so asto calculate the trigger initiation voltage V0_D. For example, if thepeak trigger voltage VC is equal to 900 units of voltage, the peaktrigger voltage VD of the peak D may be estimated to be 870 units ofvoltage, and thus the trigger initiation voltage V0_D may be set to 770units of voltage (i.e., 870 minus the predefined voltage value 100). Inanother embodiment, the peak trigger voltage VD of the peak D may beestimated according to the peak trigger voltages VB and VC in the samemeasurement period. For example, if the peak trigger voltage VB is 100units of voltage and the peak trigger voltage VC is 90 units of voltage,the peak trigger voltage VD of the peak D may be estimated to beapproximately equal to 80 units of voltage, so as to set the triggerinitiation voltage V0_D to 70 units of voltage for detecting the actualpeak trigger voltage VD.

In general, if the oscillation cycle corresponding to the peak D in theprevious measurement period is not measured, the data of the previouspeak trigger voltage corresponding to the peak D may be generated from ameasurement result obtained long time ago. However, the power supplyprocess of the induction type power supply system 100 may possessvariations on loading and/or output power, which generate significantvariations on the peak voltages of the coil signal C1, and thesevariations may be up to tens or hundreds of times. In such a condition,the peak trigger voltage obtained long time ago may not be a usefulreference. Therefore, a more appropriate trigger initiation voltage maybe obtained by using the peak trigger voltage of the previousoscillation cycle in the same measurement period as a basis, in order toincrease the probability of successful trigger to obtain the attenuationparameter and the determination result of intruding metal.

Please note that, in the abovementioned methods, the trigger signal maynot appear to successfully obtain an attenuation parameter in everymeasurement period. If a trigger signal does not appear and thecorresponding peak trigger voltage is not obtained in an oscillationcycle, the processor 111 may discard the calculation and determinationresult in the measurement period and also decrease the triggerinitiation voltage to increase the probability of successful trigger inthe next measurement period. In addition, in order to effectively obtainthe peak trigger voltage, the processor 111 may measure the resonantfrequency of the coil in advance and obtain a region in each resonantcycle where the peak may appear. If there is no trigger appearing inthis region, the trigger initiation voltage may be too high; hence, theprocessor ill decreases the trigger initiation voltage in the nextmeasurement period and retries to generate a trigger signal to obtainthe corresponding peak trigger voltage.

As can be seen, the present invention aims at measuring the coil signalduring the measurement period where the driving signals are interruptedto obtain the peak trigger voltages corresponding to a plurality of peakvalues and calculate the attenuation parameter according to the ratio ofthe average of two adjacent peak trigger voltages relative thedifference of the two peak trigger voltages, in order to compare theattenuation parameter with the corresponding threshold value todetermine whether it is necessary to obtain more peak trigger voltagesof the peaks for follow-up determination, and thereby performdetermination on intruding metal. The processor may set the referencevoltage to be equal to a trigger initiation voltage and control thereference voltage to rise gradually when a trigger appears, so as toobtain the peak trigger voltage. Those skilled in the art may makemodifications and alternations accordingly. For example, in the aboveembodiments, there are at most 5 oscillation cycles measured to obtain 5peak trigger voltages and calculate 4 attenuation parameters in ameasurement period. In another embodiment, the maximum number ofmeasured oscillation cycles and the maximum number of obtainedattenuation parameters may be adjusted according to system requirements,and should not be limited herein. In addition, in the above embodiments,the values of the peak trigger voltages and the trigger initiationvoltages are merely examples, and those skilled in the art may set andobtain appropriate voltage values according to system requirements. Forexample, the voltage generator 113 may be realized with a DAC, and theabovementioned units of voltage may be digital values configured by theprocessor 111 and converted into corresponding analog voltages and thenoutputted by the DAC. The peak trigger voltages and the triggerinitiation voltages may be configured with different values fordifferent types or resolutions of the DAC. For example, if the voltagegenerator 113 is a 12-bit DAC, it may receive digital values between0-4095 and correspondingly generate an output voltage according to theoperating voltage range of the coil signal C1 (after passing through thevoltage dividing circuit 130). In addition, the peak trigger voltage isa voltage level obtained when the reference voltage rises to the end ofthe trigger signal from the trigger initiation voltage, and theprocessor 111 may adjust the rising speed of the reference voltage. Forexample, the processor 111 may control the reference voltage to risewith a fixed speed and the rising speed is adjust to an optimal value,so that the voltage level at the end of the trigger signal is able toeffectively reflect the peak voltage level.

The intruding metal detection method of the present invention mayeffectively decrease the interrupting time of the driving signals, toreduce the influence of driving interrupt on the power supply function.Therefore, the determination process of intruding metal should befinished within the least possible time. In the above embodiment, only 2oscillation cycles in minimum are measured to accomplish thedetermination of intruding metal. In addition to the discardedoscillation cycle of the first peak, the driving signal needs to beinterrupted within the period of three oscillation cycles to the leastextent. In another embodiment, the interrupting time of the drivingsignals may further be reduced.

Please refer to FIG. 8, which is a schematic diagram of anotherintruding metal detection process 80 according to an embodiment of thepresent invention. As shown in FIG. 8, the intruding metal detectionprocess 80, which may be utilized in a supplying-end device of aninduction type power supply system such as the supplying-end module 1 ofthe induction type power supply system 100 shown in FIG. 1, includes thefollowing steps:

Step 800: Start.

Step 802: Obtain a previous peak trigger voltage measured during aprevious measurement period and set the reference voltage to be equal tothe previous peak trigger voltage.

Step 804: Interrupt the driving signals D1 and D2 of the induction typepower supply system 100 to stop driving the supplying-end coil 16 duringa measurement period, to generate a coil signal C1 of the supplying-endcoil 16.

Step 806: Measure a first peak of the coil signal C1 within anoscillation cycle of the coil signal C1, to obtain a first peak triggervoltage.

Step 808: Compare the first peak trigger voltage with the referencevoltage and determine whether the first peak trigger voltage is equal toor close to the reference voltage. If yes, go to Step 810; otherwise, goto Step 812.

Step 810: Determine that there is no intruding metal 3 existing in apower supply range of the induction type power supply system 100, andthen go to Step 818.

Step 812: Measure a second peak of the coil signal C1 within the nextoscillation cycle of the coil signal C1, to obtain a second peak triggervoltage.

Step 814: Calculate an attenuation parameter according to the first peaktrigger voltage and the second peak trigger voltage.

Step 816: Compare the attenuation parameter with a threshold value todetermine whether there is an intruding metal 3 existing in the powersupply range of the induction type power supply system 100.

Step 818: End.

The difference between the intruding metal detection process 80 and theintruding metal detection process 20 is that, in the intruding metaldetection process 80, the processor 111 only needs to measure one peakof the coil signal C1 and obtain one peak trigger voltage in minimumduring the measurement period where the driving signals D1 and D2 areinterrupted, to realize the determination of intruding metal 3.

For example, please refer to FIG. 9, which is a schematic diagram ofperforming determination on intruding metal using a peak trigger voltageVB during a measurement period according to an embodiment of the presentinvention. As shown in FIG. 9, the coil signal C1 only includes twopeaks A and B in the measurement period. Similarly, in order to preventthat determination of the intruding metal 3 is influenced by the drivingsignals D1 and D2 and thus gets distorted, the measurement of the peaktrigger voltage of the peak A may be omitted. Subsequently, in theoscillation cycle corresponding to the peak B, the processor 111 may setthe reference voltage to be equal to a trigger initiation voltage V0_B,and obtain the peak trigger voltage VB corresponding to the peak Baccording to the above method.

Please note that, in the previous measurement period, the processor 111may measure a previous peak trigger voltage corresponding to the presentpeak trigger voltage VB in advance, i.e., the peak trigger voltage VBcorresponding to the peak B in the previous measurement period, andstore the previous peak trigger voltage VB as a reference voltage. Forexample, the processor 111 may store the reference voltage in a memory.In addition, in the previous measurement period, only the peak triggervoltage VB is obtained and the determination result indicates that thereis no intruding metal 3, or only the peak trigger voltages VB and VC areobtained in the previous measurement period and the calculated firstattenuation parameter PAR1 is greater than the first threshold value TH1to indicate that there is no intruding metal 3. Subsequently, in thepresent measurement period, the processor 111 only needs to obtain thepeak trigger voltage VB corresponding to the peak B and thedetermination of the intruding metal 3 may be realized. In detail, theprocessor 111 may compare the peak trigger voltage VB with the referencevoltage. When the peak trigger voltage VB is equal to or close to thereference voltage, the processor 111 may determine that there is nointruding metal 3 existing in the power supply range of the inductiontype power supply system 100. In such a condition, after measurement ofthe peak trigger voltage VB is complete, the power driver units 121 and122 may be reconnected to control the driving signals D1 and D2 to drivethe supplying-end coil 16 to output power.

In general, when no intruding metal 3 exists and the statuses of theoutput power of coil and the loading do not change, the peak triggervoltage VB corresponding to the peak B does not change substantially. Onthe contrary, when an intruding metal 3 enters the power supply range ofthe induction type power supply system 100, the peak trigger voltage VBmay significantly fall due to the intruding metal 3 if other conditions(such as the output power of coil and the loading) remain consistent. Insuch a condition, the processor 111 only needs to measure the peaktrigger voltage VB to accomplish the determination of the intrudingmetal 3. As a result, during the measurement period where the drivingsignals D1 and D2 are interrupted, only 2 oscillation cycles areincluded in minimum, wherein the oscillation cycle corresponding to thepeak A is not measured. After measurement of the oscillation cyclecorresponding to the peak B is accomplished to obtain the peak triggervoltage VB, the determination of intruding metal 3 may be realized bycomparing the peak trigger voltage VB with the reference voltageobtained previously.

In an embodiment, when the peak trigger voltage VB is determined to beequal to or close to the reference voltage, there may be no intrudingmetal 3 existing in the power supply range of the induction type powersupply system 100. At this moment, the processor 111 may update thestored reference voltage and set the reference voltage to be equal tothe present peak trigger voltage VB, which is used for the determinationin the subsequent measurement period.

Please note that the above determination of “equal to or close to” maybe performed in any manner. For example, if the peak trigger voltage VBis within a specific range around the reference voltage, these twovoltages are determined to be equal to or close to each other. In anexemplary embodiment, the processor 111 may configure that the regionbetween the level of the reference voltage plus 50 units of voltage andthe level of the reference voltage minus 50 units of voltage isconsidered as close to the reference voltage, and the reference voltageobtained in the previous measurement period is equal to 1000 units ofvoltage. In such a condition, if the peak trigger voltage VB is withinthe range of 950-1050 units of voltage, the processor 111 may determinethat the peak trigger voltage VB is equal to or close to the referencevoltage, and thereby determine that no intruding metal 3 exists. Inanother embodiment, the range above or below the reference voltagewithin a specific ratio may be considered as equal to or close to thereference voltage. In an exemplary embodiment, the region between thereference voltage plus five percents and the reference voltage minusfive percents is considered as close to the reference voltage, and thereference voltage obtained in the previous measurement period is equalto 500 units of voltage. In such a condition, if the peak triggervoltage VB is within the range of 475-525 units of voltage, theprocessor 111 may determine that the peak trigger voltage VB is equal toor close to the reference voltage, and thereby determine that nointruding metal 3 exists.

In addition, if the peak trigger voltage VB is determined to be notequal to or close to the reference voltage in the present measurementperiod, there may be an existing intruding metal 3 or a variation ofoutput power and/or loading in the system. At this moment, the processor111 should further measure the next oscillation cycle of the coil signalC1 and obtain the corresponding peak trigger voltage. Subsequently, theprocessor ill may calculate an attenuation parameter according to thepeak trigger voltages measured in two adjacent oscillation cycles, andcompare the attenuation parameter with the corresponding threshold valueto perform determination on the intruding metal 3. In other words, inthe intruding metal detection process 80, if a first peak triggervoltage (e.g., VB) is determined to be not equal to or close to thereference voltage, the next oscillation cycle should be measured toobtain a second peak trigger voltage (e.g., VC shown in FIG. 4), toperform subsequent determination of the intruding metal 3, and thisdetermination may be realized with the abovementioned intruding metaldetection process 20 shown in FIG. 2.

Please note that, in a special case, the peak trigger voltage VB may beequal to or close to the reference voltage while the intruding metal 3approaches and the influence is cancelled by movement of the coil orvariation of the load. In order to prevent that the intruding metal 3may not be successively determined in this situation, the processor illmay set an upper limit for the consecutive number of times or theduration period where the peak trigger voltage VB is determined to beequal to or close to the reference voltage. When the consecutive numberof times or the duration period reaches the upper limit, the steps ofmeasuring the next oscillation cycle to obtain a second peak triggervoltage (e.g., VC shown in FIG. 4) and calculating the attenuationparameter are performed; that is, to perform determination on theintruding metal 3 using the above intruding metal detection process 20shown in FIG. 2. In an embodiment, the processor 111 may include acounter, for calculating the consecutive number of times the peaktrigger voltage VB is determined to be equal to or close to thereference voltage and thus only the peak trigger voltage VB is measured.The intruding metal detection process 20 shown in FIG. 2 is performedwhen the counter reaches the upper limit. At this moment, the processor111 resets the counter to recalculate the consecutive number of times.Alternatively, the processor 111 may include a timer, for determiningthe duration period where the peak trigger voltage VB is determined tobe equal to or close to the reference voltage. The intruding metaldetection process 20 shown in FIG. 2 is performed when the timerexpires. At this moment, the processor 111 resets the timer torecalculate the duration period. Alternatively, the determination resultof the peak trigger voltage VB is not considered in the operations ofthe timer. For example, the timer may operate periodically based on aspecific fixed timing. The intruding metal detection process 80 shown inFIG. 8 is applied in usual, and the intruding metal detection process 20shown in FIG. 2 is compulsorily performed when the timer expires.

To sum up, the present invention provides an intruding metal detectionmethod which is capable of measuring coil signals to obtain one or morepeak trigger voltages during the measurement period where drivingsignals are interrupted. The processor may compare the peak triggervoltage with a reference voltage obtained previously to performdetermination on intruding metal, or calculate the attenuation parameteraccording to the ratio of the average of two adjacent peak triggervoltages relative to the difference of the two peak trigger voltages.The processor then compares the attenuation parameter with thecorresponding threshold value to determine whether to obtain subsequentpeak trigger voltages of other peaks for follow-up determination, so asto realize the determination of intruding metal. The processor may setthe reference voltage to be equal to a trigger initiation voltage with alower level, and control the reference voltage to rise gradually when atrigger appears, so as to obtain the peak trigger voltage. Setting thetrigger initiation voltage to a lower level may increase the probabilityof successful trigger to obtain the peak trigger voltage. In addition,when there is no existing intruding metal, the intruding metal detectionmethod of the present invention only needs to measure one or two coiloscillation cycles and correspondingly obtains one or two peak triggervoltages in minimum, to realize the determination of intruding metal.With the additional first peak without measurement, the measurementperiod where driving signals are interrupted may include 2-3 coiloscillation cycles to the least extent, and the influence on poweroutput function from the interrupted driving signals may besignificantly reduced. In addition, the intruding metal detection methodof the present invention may perform the determination based on theattenuation ratio of the coil signal, which replaces the determinationmethod of using the attenuation quantity or the attenuation slope in theprior art, so as to solve the problems where the determination based onthe attenuation slope is easily influenced by the coil amplitude andloading.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An intruding metal detection method for asupplying-end module of an induction type power supply system, thesupplying-end module comprising a supplying-end coil, the intrudingmetal detection method comprising: interrupting at least one drivingsignal of the induction type power supply system to stop driving thesupplying-end coil during a measurement period, to generate a coilsignal of the supplying-end coil; measuring a plurality of peaks of thecoil signal within a plurality of consecutive oscillation cycles of thecoil signal, to obtain a plurality of peak trigger voltages,respectively; calculating a first attenuation parameter according to afirst peak trigger voltage and a second peak trigger voltage among theplurality of peak trigger voltages; and comparing the first attenuationparameter with a first threshold value to determine whether there is anintruding metal existing in a power supply range of the induction typepower supply system.
 2. The intruding metal detection method of claim 1,wherein the step of calculating the first attenuation parameteraccording to the first peak trigger voltage and the second peak triggervoltage among the plurality of peak trigger voltages comprises:calculating the first attenuation parameter according to a ratio of anaverage of the first peak trigger voltage and the second peak triggervoltage relative to a difference of the first peak trigger voltage andthe second peak trigger voltage.
 3. The intruding metal detection methodof claim 1, wherein the first attenuation parameter is equal to asummation result of the first peak trigger voltage and the second peaktrigger voltage divided by a subtraction result of the first peaktrigger voltage and the second peak trigger voltage.
 4. The intrudingmetal detection method of claim 1, wherein the first peak triggervoltage is close to and lower than a peak voltage of a correspondingfirst peak among the plurality of peaks, and the second peak triggervoltage is close to and lower than a peak voltage of a correspondingsecond peak among the plurality of peaks.
 5. The intruding metaldetection method of claim 1, wherein the step of measuring the pluralityof peaks of the coil signal within the plurality of consecutiveoscillation cycles of the coil signal to obtain the plurality of peaktrigger voltages, respectively, comprises: performing the followingsteps during one of the plurality of oscillation cycles: setting areference voltage to be equal to a trigger initiation voltage;controlling the reference voltage to rise gradually after a triggersignal appears; and obtaining a level of the reference voltage at theend of the trigger signal as a peak trigger voltage among the pluralityof peak trigger voltages.
 6. The intruding metal detection method ofclaim 5, wherein the step of measuring the plurality of peaks of thecoil signal within the plurality of consecutive oscillation cycles ofthe coil signal to obtain the plurality of peak trigger voltages,respectively, further comprises: obtaining a corresponding firstprevious peak trigger voltage generated during a previous measurementperiod, and setting the trigger initiation voltage to a value equal tothe first previous peak trigger voltage minus a predefined voltagevalue; or performing the following steps when the corresponding firstprevious peak trigger voltage is not generated during the previousmeasurement period: obtaining a second previous peak trigger voltagewithin a previous oscillation cycle among the plurality of oscillationcycles; calculating a predicted peak trigger voltage according to thesecond previous peak trigger voltage; and setting the trigger initiationvoltage to a value equal to the predicted peak trigger voltage minus thepredefined voltage value.
 7. The intruding metal detection method ofclaim 1, wherein the step of comparing the first attenuation parameterwith the first threshold value to determine whether there is anintruding metal existing in the power supply range of the induction typepower supply system comprises: determining that there is no intrudingmetal existing in the power supply range of the induction type powersupply system when the first attenuation parameter is greater than thefirst threshold value; and performing the following steps when the firstattenuation parameter is smaller than the first threshold value:obtaining a third peak trigger voltage among the plurality of peaktrigger voltages; calculating a second attenuation parameter accordingto the second peak trigger voltage and the third peak trigger voltage;and comparing the second attenuation parameter with a second thresholdvalue.
 8. The intruding metal detection method of claim 7, wherein thefirst threshold value is obtained by adding a first value to a defaultbasic threshold value, and the second threshold value is obtained byadding a second value to the basic threshold value, wherein the secondvalue is smaller than the first value.
 9. The intruding metal detectionmethod of claim 1, further comprising: calculating a plurality ofattenuation parameters according to the plurality of peak triggervoltages; and averaging the plurality of attenuation parameters todetermine whether there is an intruding metal existing in the powersupply range of the induction type power supply system.
 10. Theintruding metal detection method of claim 9, wherein the step ofaveraging the plurality of attenuation parameters to determine whetherthere is an intruding metal existing in the power supply range of theinduction type power supply system comprises: obtaining an averageresult generated by averaging the plurality of attenuation parameters;comparing the average result with a basic threshold value; determiningthat there is no intruding metal existing in the power supply range ofthe induction type power supply system when the average result isgreater than the basic threshold value; and determining that there is anintruding metal existing in the power supply range of the induction typepower supply system when the average result is smaller than the basicthreshold value.
 11. A supplying-end module for an induction type powersupply system for performing an intruding metal detection method, thesupplying-end module comprising: a supplying-end coil; a resonantcapacitor, coupled to the supplying-end coil, for performing resonancetogether with the supplying-end coil; at least one power driver unit,coupled to the supplying-end coil and the resonant capacitor, forsending at least one driving signal to the supplying-end coil to drivethe supplying-end coil to generate energies, and interrupting the atleast one driving signal to stop driving the supplying-end coil during ameasurement period to generate a coil signal of the supplying-end coil;a signal receiver, coupled to the supplying-end coil, for receiving thecoil signal from the supplying-end coil; and a processor, coupled to thesignal receiver, for performing the following steps: measuring aplurality of peaks of the coil signal within a plurality of consecutiveoscillation cycles of the coil signal, to obtain a plurality of peaktrigger voltages, respectively; calculating a first attenuationparameter according to a first peak trigger voltage and a second peaktrigger voltage among the plurality of peak trigger voltages; andcomparing the first attenuation parameter with a first threshold valueto determine whether there is an intruding metal existing in a powersupply range of the induction type power supply system.
 12. Thesupplying-end module of claim 11, wherein the processor calculates thefirst attenuation parameter according to a ratio of an average of thefirst peak trigger voltage and the second peak trigger voltage relativeto a difference of the first peak trigger voltage and the second peaktrigger voltage.
 13. The supplying-end module of claim 11, wherein thefirst attenuation parameter is equal to a summation result of the firstpeak trigger voltage and the second peak trigger voltage divided by asubtraction result of the first peak trigger voltage and the second peaktrigger voltage.
 14. The supplying-end module of claim 11, wherein thefirst peak trigger voltage is close to and lower than a peak voltage ofa corresponding first peak among the plurality of peaks, and the secondpeak trigger voltage is close to and lower than a peak voltage of acorresponding second peak among the plurality of peaks.
 15. Thesupplying-end module of claim 11, wherein the processor performs thefollowing steps to measure the plurality of peaks of the coil signalwithin the plurality of consecutive oscillation cycles of the coilsignal to obtain the plurality of peak trigger voltages, respectively:performing the following steps during one of the plurality ofoscillation cycles: setting a reference voltage to be equal to a triggerinitiation voltage; controlling the reference voltage to rise graduallyafter a trigger signal appears; and obtaining a level of the referencevoltage at the end of the trigger signal as a peak trigger voltage amongthe plurality of peak trigger voltages.
 16. The supplying-end module ofclaim 15, wherein the processor further performs the following steps tomeasure the plurality of peaks of the coil signal during the pluralityof consecutive oscillation cycles of the coil signal to obtain theplurality of peak trigger voltages, respectively: obtaining acorresponding first previous peak trigger voltage generated during aprevious measurement period, and setting the trigger initiation voltageto a value equal to the first previous peak trigger voltage minus apredefined voltage value; or performing the following steps when thecorresponding first previous peak trigger voltage is not generatedduring the previous measurement period: obtaining a second previous peaktrigger voltage within a previous oscillation cycle among the pluralityof oscillation cycles; calculating a predicted peak trigger voltageaccording to the second previous peak trigger voltage; and setting thetrigger initiation voltage to a value equal to the predicted peaktrigger voltage minus the predefined voltage value.
 17. Thesupplying-end module of claim 11, wherein the processor performs thefollowing steps to compare the first attenuation parameter with thefirst threshold value to determine whether there is an intruding metalexisting in the power supply range of the induction type power supplysystem: determining that there is no intruding metal existing in thepower supply range of the induction type power supply system when thefirst attenuation parameter is greater than the first threshold value;and performing the following steps when the first attenuation parameteris smaller than the first threshold value: obtaining a third peaktrigger voltage among the plurality of peak trigger voltages;calculating a second attenuation parameter according to the second peaktrigger voltage and the third peak trigger voltage; and comparing thesecond attenuation parameter with a second threshold value.
 18. Thesupplying-end module of claim 17, wherein the first threshold value isobtained by adding a first value to a default basic threshold value, andthe second threshold value is obtained by adding a second value to thebasic threshold value, wherein the second value is smaller than thefirst value.
 19. The supplying-end module of claim 11, wherein theprocessor further performs the following steps: calculating a pluralityof attenuation parameters according to the plurality of peak triggervoltages; and averaging the plurality of attenuation parameters todetermine whether there is an intruding metal existing in the powersupply range of the induction type power supply system.
 20. Thesupplying-end module of claim 19, wherein the processor performs thefollowing steps to average the plurality of attenuation parameters todetermine whether there is an intruding metal existing in the powersupply range of the induction type power supply system: obtaining anaverage result generated by averaging the plurality of attenuationparameters; comparing the average result with a basic threshold value;determining that there is no intruding metal existing in the powersupply range of the induction type power supply system when the averageresult is greater than the basic threshold value; and determining thatthere is an intruding metal existing in the power supply range of theinduction type power supply system when the average result is smallerthan the basic threshold value.